(1) To collect clinical material of high potential infectivity for use in laboratory studies; (2) To develop and test in vitro procedures and animal systems for use in laboratory studies of viral hepatitis; (3) To propagate the viruses of hepatitis A and B in culture or in experimental animals; (4) To study the biochemistry, biophysics, immunology and epidemiology of hepatitis-associated antigens; (5) To develop vaccines or other control measures for viral hepatitis.